1. Field of the Invention
The present invention relates to a control apparatus which is widely used to control an industrial system in, e.g., a factory automation field such as a steel, paper, or automobile plant, including assembly operations, a process automation field such as a chemical plant, or a public utility such as a water supply and drainage system, and, more particularly, to a control apparatus which can transmit data input/output to/from an I/O or a transmission apparatus, between the control apparatus and an off-system control apparatus at high speed.
2. Description of the Related Art
As shown in FIG. 1, a conventional control apparatus 40 includes a CPU 11, program memory 12, data memory 13, control program execution circuit 14, control program memory 15, control data memory 16, I/O interface 17, communication interface 18, data transmission circuit 20, and inter-module interface 24 which are connected to each other through a system bus 19.
The CPU 11 is a processor for totally managing the control apparatus 40. The program memory 12 stores a system program (operating system) and total management software used by the CPU 11. The data memory 13 stores data used in the system program (operating system) and total management software.
The control program execution circuit 14 is a dedicated circuit for executing an application program (control program) to use the control apparatus 40. The application program (control program) executed by the control program execution circuit 14 is stored in the control program memory 15. The control data memory 16 stores the data used when executing this application program (control program), and is used as a work area.
The I/O interface 17 is a circuit for adjusting data length and data access timing in order to connect to the system bus 19 an I/O 2 connected to a control target 30. Note that the I/O 2 is an apparatus for connecting the control target 30 to the control apparatus 40. The I/O 2 is used to input the state of the control target 30, and drive the control target 30.
The communication interface 18 is a circuit for adjusting data transfer speed and timing between the control apparatus 40 and an apparatus such as a monitor apparatus 3 connected by serial data transmission.
The data transmission circuit 20 is a circuit for efficiently performing data transfer by, e.g., changing, modulating, and demodulating a data signal voltage, in order to transmit the data between the control apparatus 40 and an off-system control apparatus 23 at high speed.
The inter-module interface 24 is connected to an inter-module connection bus 25 in addition to the system bus 19. The inter-module interface 24 is an interface for transmitting/receiving the data between the control apparatus 40 and an off-system module 26 which is also connected to the inter-module connection bus 25.
The above-described control apparatus 40 is connected to the off-system module 26 through the inter-module connection bus 25. For example, if the off-system module 26 is a transmission module, a control data memory for storing a variable used in this transmission module is different from the control data memory 16 for storing an I/O control variable.
Also, a memory area used to exchange data between the control apparatus 40 and the off-system control apparatus 23 through a transmission path 22 is different from the area of the control data memory 16.
Therefore, for example, when data from the I/O 2 used by the control apparatus 40 is to be transmitted to the off-system control apparatus 23, the I/O control variable needs to be copied into the control data memory 16 for storing the transmission module variable. In addition to this, the transmission module serving as one form of the off-system module 26 is generally independent of the control apparatus 40. Hence, the data needs to be transferred between the control apparatus 40 and the module 26, thus consuming data transfer time in addition to the transmission time.
However, in the above-described conventional control apparatus, the following problem occurs.
That is, in the above-described conventional control apparatus, overhead is increased when the control variable in one storage area is transferred to a different storage area of an off-system peripheral circuit and the module 26. As a result, the increase in control speed is prevented.
The present invention has been made in consideration of this case, and has as its object to provide a control apparatus which can integrally handle not only I/O data but also a memory area used by a transmission apparatus connected to the control apparatus itself, or a module having other functions, reduce the time required for copying the control variable, and increase the speed of the control operation.